The Impact of Pre- and Post-Treatment Processes on Corrosion Resistance of Micro-Arc Oxidation Coatings on Mg Alloys: A Systematic Review

As one of the lightest metallic structural materials, magnesium (Mg) alloys possess numerous distinctive properties and are utilized across a broad spectrum of applications. However, the poor corrosion resistance of Mg alloys limits their application. Micro-arc oxidation (MAO) is an effective surface treatment method that enhances the corrosion resistance of Mg alloys. Nevertheless, the intrinsic porous structure of MAO coatings hinders significant improvement in corrosion resistance. Research indicates that the pre- and post-treatment processes associated with MAO markedly enhance the densification of the oxide coatings, thereby improving their overall performance. This paper aims to provide a comprehensive review and analysis of the effects of various pre- and post-treatment processes, highlighting key advancements and research gaps in improving MAO coatings on Mg alloys. An in-depth analysis of the crucial role of pre-treatment in optimizing interfacial bonding and post-treatment in enhancing coating density is conducted using electrochemical testing and scanning electron microscopy (SEM). Finally, the future development of pre- and post-treatment processes are discussed.